At present, generally, digital to analog converters (DACs) suitable for a display are mainly divided into a current-steering type and a resistor string voltage divider type. Although the current-steering type DAC has characteristics of high speed and high precision, when it is used for driving a signal to transmit towards a transmission line, in order to inhibit reflection of the transmitted signal, an output impedance of the current-steering type DAC must be equal to a characteristic impedance of the transmission line, resulting in a relatively large power consumption of the current-steering type DAC. On the other hand, although the resistor string voltage divider type DAC has advantages of simple structure, low noise and good linearity etc., the precision of the resistor string voltage divider type DAC is mainly determined by the match of the resistor string.
With the development of high definition display technology, the requirement on the performance of the DAC in a display becomes higher and higher, which is required above 10 bits generally. At present, the resistor string voltage divider type 10 bit DAC has a complex structure, which brings large amount of wiring issues. Moreover, the 10 bit DAC generally occupies an area up to 60%-70% in a chip, which occupies a relatively large area of the chip.
In order to solve the above problems, some 10 bit DACs using a two-stage segmented structure are put forth. Such a structure divides the 10 bit DAC into two stages. Generally, a first stage uses a global resistor string structure. Two adjacent reference voltages VL and VH are selected from the global resistor string by a voltage selector, and then, a second stage divides the two adjacent voltages obtained by the first stage accurately, so as to obtain a final analog voltage. In such a solution, although the number of switches is reduced to some extent, the number of reference voltage points is not reduced, hence, it may still render the structure thereof complex and bring large amount of wiring issues. Moreover, the occupied area is also relatively large, which is not benefit for improving competitiveness of the product.